The present disclosure relates generally to the field of semiconductor integrated circuits and, more particularly, to a shielding layer that may be used to reduce noise coupling in such circuits.
Radio frequency (RF) components are often implemented with integrated circuits (ICs) used in areas such as wireless communications systems, including Global System for Mobile Communications (GSM); Digital Enhanced Cordless Telecommunications (DECT); Universal Mobile Telecommunications System (UMTS); and bluetooth. Each system may operate within a different frequency range, but all generally involve high frequency signals.
Among other components, RF circuits frequently utilize inductors for filtering, amplifying, and decoupling DC/AC signals, as well as in impedance matching and in the formation of resonant circuits used in radio-frequency applications. For frequencies below 100 Hz, discrete off-chip inductor components may be used because of the difficulty in integrating inductors having the needed high inductance values into an IC. However, with the increased speed of IC devices and the advancement in multilevel interconnection technologies, it is becoming increasingly common to incorporate other passive components, such as resistors and inductors into ICs.
In radio frequency integrate circuits (RF ICs), crosstalk (e.g., or interference between RF passive components and underlying interconnections) generally increases as signal frequency increases. To minimize such crosstalk, a shielding structure may be used to isolate various RE circuits and to prevent noise coupling between the RF passive components and the underlying interconnections and active devices. Currently, a single, uninterrupted layer of metal may be used as a shielding layer in an RFIC chip to isolate RE passive components from metal interconnect circuits. However, such a single, uninterrupted metal layer generally violates IC design rules and is a poor use of IC surface area. Furthermore, while fabricating RF circuits on a semiconductor substrate, chemical-mechanical polishing (CMP) of such a large surface area as that formed by the metal plate may cause a “dishing” effect in which the processed metal surface is dish shaped rather than flat.
Accordingly, what is needed is improved shielding for RFICs and a method for forming such shielding.